1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly, to an InAlAs/InGaAs heterojunction field effect type semiconductor device formed on an InP substrate.
2. Description of the Related Art
A prior art heterojunction field effect type semiconductor device is constructed by an InP substrate, an InAlAs/InGaAs heterostructure formed on the InP substrate, an InAlAs Schottky layer formed on the heterojunction, and electrodes formed on the InAlAs Schottky layer. These layers are sequentially epitaxially grown. This will be explained later in detail.
The fabrication of the device, however, generally requires some thermal treatments after growth, so that the electrical quality are degraded. That is, during the thermal treatments, impurity atoms adhered to the surface of epitaxial layers are thermally diffused thereinto, to thereby deteriorate the crystalline quality of the epitaxial layers (see: N. Hayafuji et al., "Thermal Stability of AlInAs/GaInAs/InP Heterostructures" , Appl Phys. Lett. 66 (7), pp. 863-865, February 1995).